The invention related to a process for longitudinal adjustment of tools for individual working spindles of a multiple-spindle automatically controlled machine tool, in all cases on a working-part reference point as the zero point coordinate of a common processing program. The invention also relates to a device for using this process in a machine tool in which working spindles are arranged adjustably in the direction of their axes at the machine frame, and a working-part table is arranged therebelow.
In the case of numerically controlled multiple-spindle machine tools with simultaneously working work spindles, the problem arises on first introducing the tools or after each change in tools of having to adjust each of the working spindles individually to a zero-point coordinate of the common processing program. To be sure, essentially many equal tools are suitably introduced into the working spindles for simultaneous processing of the individual working parts, but in spite of a prior suitable selection these tools usually have differing lengths. Further, imprecision can arise in the holding devices for the tools whereby the individual working part reference surfaces do not exactly lie in the same plane. Different distances thus result between the lower edges of the tools and the tool reference surfaces in the starting position in which the tools are located in the program starting point and between the tools and the working parts. As these differences are considerably greater than machine processing tolerances as well as permissible measurement tolerances of finished processed working parts, special measures must be found in order to bring all the tools into a starting position with respect to the working-part reference point, which is then retained as the zero-point coordinate for the common processing program.
Determination of the zero point of a spatial coordinate system is known in the case of a milling machine for a working part clamped tightly to a machine table, in order then to bring the lower edge of the working part into a reference plane defined by coordinate axes by means of a measuring and indicating device whereby a zero-point correction is determined according to a certain scale and the tool is suitably forwarded to the working part (German Pat. No. 1,652,751). This mechanical adjustment of the tools by means of a special measuring and indicating device must be undertaken separately for each working spindle in the case of a multiple-spindle machine tool. This adjustment requires a considerable expenditure of time, which is not acceptable especially in the case of multiple-spindle machine tools with automatic tool exchange as well as where there are short tool-change times with frequent changes of tools, because the time advantage achieved by the automatic tool exchange again would be lost. In addition, errors can creep in during the forwarding of the individual tools in relation to the working part involved, whereby the known process is not substantially more reliable than is measuring the interval differences between the tools and the working-part reference points or surfaces by hand, as hitherto generally was done.
Furthermore, a device is known for obtaining tool-dependent correction values for positioning action of a numerically controlled machine tool, in which a known calibration position is provided in the position within the machine coordinate system in the form of a measuring stop which is startable and program-controlled by the tool (German Pat. No. 1,957,577). However, this device is suitable only for the precise positioning of a single tool, and it therefore cannot be transferred simply for all working spindles by multiplying for a multiple-spindle machine tool with a simultaneous processing program. Finally, it is very important in the case of such multiple-spindle machine tools particularly to consider the dependence of the control of the individual working spindles by way of common slides or swinging baskets.
The goal of the present invention therefore was to propose a process for the longitudinal adjustment of tools from individual working spindles of a multiple-spindle automatically controlled machine tool which, with working spindles controlled in dependence on each other, permits an automatic positioning (as simultaneously as possible) of the individual working spindles or the tools taken up by them in relation to the individual working-part reference points or surfaces. With a view to a high adjustment precision of the individual tool positions, the last runnings of the individual working spindles on switching off when the predetermined position is reached should be insignificantly small.